What are the best books that elaborate the aims of Qur'anic surahs?

In a Nutshell: If you want a quick discussion, I would suggest "ibn Ashur, al-Tahreer wa al-Tanweer," but for more scholarly detailed discussion I would recommend a long list and most importunately "Sayd Qutb, fi Dhilal al-Qur'an." For learning the principles of deducing the aims of surahs, I would recommend "Farahi, Dala'il al-Nidham. Background The search for aims of surahs (maqasid al-suwar) is the best, but hardest, method to reach the beauty and the real message of the Qur'an and to live its meaning. But still, it is a very hard, but achievable, task. One of the best scholars wrote in maqasid of the surahs is al-Farahi who argued it is the most difficult field: أصعب المعارف ويحتاج إلى شدة التأمل والتمحيص "It is the hardest field of Knowledge and it needs intense reflection and scrutiny." (Farahi, Dala'il al-Nidham, p. 16) Similarly argued by Biqa'i in Qatf al-Azhaar, Vol. 2, p. 108. Books of Maqasi Al-Suwar There are a number of books focused only on the maqasid of the surahs as well as a number of tafsirs gave some attention to such field. I will include a number of these works and I am going to classify them into three main categories to make it easier for readers to achieve their aims from reading. Simple work: If you are interested in reading the summary of the surahs with some quick insights, I would suggest: Ibn Ashur, al-Tahreer wa al-Tanweer: The author mentions briefly at the beginning of each surah the main issues discussed and the main aims of revealing such a surah. This would be enough of a reader who seeks only a nutshell. The two books of Biqa'i are also useful but more comprehensive: His tafsir (Nadhm al-Durar) gave a great but concise discussion on the maqasid of the surahs of the Qur'an at the beginning of each surah. It also summarises the topics discussed in the surah; Masa'id al-Nadhar is a summary of his tafsir's insights. Scholarly Detailed Discussions: If you are looking for deeper discussions and more fundamental insights, I would suggest the followings (in that order): Sayd Qutb, fi Dhilal al-Qur'an: It is the best book discusses comprehensively the main aims of the surah at its beginning. It is very special and thoughtful. Sabuni, Qabs min Noor al-Qur'an al-Kareem: It is also a specialised study in the field that is interesting as it only focusses on the maqasid and connection between verses and surahs. It is also a primary source that spent a great time digging in the classical books of tafsir. (Unfortunately, I am only able to review the first two volumes from al-Fatihah to al-Ma'idah) Tafsir al-Maraghi: It also mentions great discussion at the end of each surah for the aims of surahs and the beauty of the orders of surahs as well as the verses. Sa'eed Hawa, al-Asas fi al-Tafsir: It includes a thoughtful and accumulative review of classical mufaseroon's insights and well as the authors own contribution. Ibn al-Zubayr, al-Burhan fi Tanasub Suwar al-Qur'an: It focuses mainly on the connective meanings between the following surahs in a way elaborates the maqasid of each surah as well. Fairuzabadi, Basa'ir Dhawi al-Tameez: It gives an introduction of each surah and one or two pages on its discussed subjects and the aims of them. Zuhili, al-Tafsir al-Muneer: It is a contemporary tafsir that could be distinguished by putting headings for of given verses that discuss a certain topic and a good elaboration for the maqasid at the beginning of each surah. Dr Abdullah Shihatah, Ahdaf Kul Surah wa Maqasiduha: It is good on deducing the aim of the surah from the names given to it as well as the helpful discussions of other mufasiroon and insights derived from connecting the meanings of the verses together. Hibnikah, Ma'alim al-Tafakur: it is a huge work provides a very profound discussion of lessons and aims deduced from the surahs at the beginning of the tafsir of each surah. Books of the Methods If you want to learn how to deduce the maqasid by yourself, I would suggest reading in the tafsirs and all (or most) of the above works as a guide after reading the following works that theorise the notion: The key book in this field, in term of learning how to deduce the aims, is the work of the contemporary mufasir al-Farahi in his book Dala'il al-Nidham. He gives the principles of deducing the general meaning and the main purpose of the surah. He also gives brief examples of all the surahs' maqasid. Dr Rabi'ah, an assistant Professor at Quseem University, also compiled a very short book, called Ilm maqasid al-Suwar, focusses on the main principles deduced from the works of classical mufasiroon. Conclusion If you want a quick discussion, I would suggest "ibn Ashur, al-Tahreer wa al-Tanweer," but for more scholarly detailed discussion I would recommend a long list and most importunately "Sayd Qutb, fi Dhilal al-Qur'an." For learning the principles of deducing the aims of surahs, I would recommend "Farahi, Dala'il al-Nidham.